Ok. I get regexp from here (only WWW links, second version). Everything is fine, except one thing, it parse BBCode too.
Regexp
(?i)\b((?:https?://|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))
What fails
[img]http://example.foo/something.png[/img]
When I apply regexp I get http://example.foo/something.png[/img and that's fail. :P Any regexp guru there?